The present invention is directed to providing novel electrodeposited superplastic alloys preferably containing at least one metal from the fourth period of Group VIII of the Periodic Table.
Superplastic alloy formed of Ti-6Al-4V is known and described by Collins and Highberger in "Superplastic Forming/Diffusion Bonding: An Update", Metal Progress, pp. 79-83 (March, 1981). The criticality of fine grain size or large grain boundary area to superplastic properties is set forth in the article. The products are wrought and require temperatures in excess of 1500.degree. F. for superplastic forming.
It has been known that nickel can be electroplated alone or with othe rmetal ions, with nickel-cobalt alloys being dominant. The comparatively low recrystallization temperature, i.e., about 700.degree. F., results in pure nickel deposits in grain growth at a temperature below which superplastic grain boundary movement can occur. Emphasis in the instance of nickel alloy deposits has been to form bright deposits through the addition of additives which reduce ductility or tensile elongation.
To this end conventional plating solutions contain varying amounts of many impurities needed to form bright deposits. While emphasis has been placed upon developing additional agents that will allow the deposits to tolerate the presence of the impurities, no effort has been made to remove them.
The impurities are introduced from many sources. Examples are impurities inherent in the metal salts, impurities introduced as the anode corrodes, impurities introduced by the cathode which are carried over as "drag-out" from a prior bath, impurities from the water, and even impurities from airborne sources. All can contribute to forming nickel and nickel alloy deposits with reduced grain boundary plasticity and increase as deposited grain size.